This application is based on Japanese Patent Application Nos. 11-241142 filed Aug. 27, 1999, and 2000-227446 filed Jul. 27, 2000, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a mold assembly for forming an ophthalmic lens article and a method of forming the same using the mold assembly. More particularly, the present invention is concerned with such a mold assembly suitably used for forming the ophthalmic lens article including an ophthalmic lens and an intermediate product for the ophthalmic lens, and such a method for forming the ophthalmic lens article using the mold assembly.
2. Discussion of Related Art
There are known methods for producing a so-called ophthalmic lens article such as ophthalmic lenses, which include contact lenses and intraocular lenses, or an intermediate product for the ophthalmic lens, which includes a lens blank having one of opposite surfaces with a configuration which follows that of a corresponding one of front and back surfaces of the intended lens while the other surface needs to be cut to form the other of the front and back surfaces of the lens. One method used to form the above-discussed lens products includes the steps of: (a) preparing a mold assembly consisting of a first mold and a second mold in the form of a male mold and a female mold or an upper mold and a lower mold, which are closed or assembled together so as to define therebetween a mold cavity having a configuration following that of the intended ophthalmic lens article; (b) polymerizing a suitable polymeric material which fills the mold cavity defined between the first and second molds, so as to form the intended ophthalmic lens article in the mold cavity; and (c) separating the first and second molds from each other, so as to remove the ophthalmic lens article formed in the mold cavity from the mold assembly.
In the method described above, since the ophthalmic lens article in the form of a polymerized product, which is obtained by polymerization of the polymeric material in the mold cavity, adheres to one of the first and second molds, the ophthalmic lens article is held on the above-indicated one of the two molds when they are removed away from each other. It is, however, quite difficult to predict on which of the two molds the formed ophthalmic lens article will be held since there is no consistency as to which of the two molds the ophthalmic lens article will be held. Moreover, it is impossible to control the formed ophthalmic lens article to be held on and adhere to a desired one of the two molds.
Accordingly, it is conventionally required to check on which of the two molds the formed ophthalmic lens article is held when the two molds are separated away or moved apart from each other, considerably deteriorating production efficiency of the ophthalmic lens article. Since the ophthalmic lens article does not consistently remain on and adhere specifically to one of the first and second molds, it is quite difficult to automate a process of removing the formed ophthalmic lens article from the mold assembly. Accordingly, the ophthalmic lens article cannot be manufactured in an automated manner. If the intermediate product for the ophthalmic lens article adheres to either one of the two molds at one of it""s the mold""s opposite surfaces, it will be necessary to determine which surface needs to be processed to provide the corresponding one of the front and back surfaces of the intended ophthalmic lens article. In order to accomplish this, the intermediate product needs to be first removed from the mold, and then held and supported by a suitable holder for processing the above-indicated surface which has adhered to the mold. This undesirably deteriorates the production efficiency of the ophthalmic lens article.
In view of the above, there have been recently proposed various techniques which permit the formed ophthalmic lens article to be held on and adhered to a predetermined one of the first and second molds of the mold assembly when the first and second molds are separated away from each other.
One example of such techniques is JP-A-7-80860, which discloses a mold assembly consisting of a male mold and a female mold for forming an intermediate product for a contact lens. The male mold of the mold assembly disclosed in this publication has a protrusion or a recess formed in its molding surface having a profile following that of a back surface of the contact lens, in an attempt to improve an adhesive strength of the molding surface for holding the molded intermediate product thereon. When the intermediate product is formed by using the thus constructed mold assembly, the molded intermediate product adheres to and is held on the male mold every time when the two molds are separated away from each other. The male mold, however, inevitably has a complicated shape due to provision of the protrusion or recess on its molding surface, as compared with a male mold without such a protrusion or recess. In the mold assembly disclosed in the above publication, the shape of the male mold is undesirably limited to a specific design which permits the protrusion or recess to be formed on its molding surface, making it difficult to form the contact lens having an intended configuration. JP-A-7-195558 discloses a mold assembly consisting of a male mold and a female mold for forming a contact lens, wherein a region of a molding surface of at least one of the male and female molds is pre-treated by corona-discharging, such that the region of the molding surface interposed between a pair of electrodes is subjected to a corona discharge, for thereby improving an adhesive strength of the molding surface for holding the formed contact lens thereon. In the thus constructed mold assembly, the formed contact lens adheres to and is held on one of the male and female molds having the pre-treated molding surface every time when the male and female molds are separated away from each other.
Unlike the mold assembly disclosed in JP-A-7-80860 wherein the molding surface of the male mold is formed into a specific shape having the protrusion or recess as described above, the mold assembly of JP-A-7-195558, wherein the molding surfaces of the male and female molds do not have such a protrusion or recess, permits the ophthalmic lens article to be formed into a desired configuration.
In the mold assembly disclosed in JP-A-7-195558, however, an expensive corona-discharge device is used for pre-treating the molding surface of at least one of the male and female molds to improve the adhesive strength of the molding surface for holding the formed contact lens thereon. For effecting the pre-treatment on the molding surface of the at least one mold with high efficiency, the electrodes are shaped to follow the configuration of the mold, so that the electrodes can be positioned as close as possible to the mold. Accordingly, the arrangement disclosed in the publication undesirably pushes up the cost of manufacture of the contact lens due to the use of the expensive corona-discharge device and the specially prepared electrodes. In a series of process steps for the pre-treatment on the molding surface of the at least one mold, it is cumbersome to position the electrodes as close as possible to the mold. In addition, if the electrodes contacted the molding surface, the molding surface would be damaged. Moreover, the pre-treatment on the molding surface of the mold is effected by applying a considerably high voltage to the electrodes, causing a risk of injuring the workers who are engaged in the pre-treatment operation.
The present invention was made in the light of the background art described above. It is a first object of the present invention to provide a mold assembly consisting of a first mold and a second mold for forming an ophthalmic lens article, wherein the ophthalmic lens article formed in the mold assembly adheres to and is held on a molding surface of a predetermined one of the first and second molds with high reliability every time the two molds are separated away from each other. The molding surface of the predetermined mold is pre-treated for holding the ophthalmic lens article thereon, at a relatively reduced cost and in a safe and easy manner without a risk of damaging the molding surface, so that the intended ophthalmic lens article can be formed at a minimized cost with high production efficiency without complicating the structure of the mold assembly.
It is a second object of the invention to provide a method of forming an ophthalmic lens article having an intended configuration at a minimized cost with high production efficiency.
As a result of an extensive study by the inventors of the present invention, it has been found that the ophthalmic lens article such as a contact lens molded in the mold assembly of a resin structure adheres to the surface of the mold assembly with high stability if the surface has been irradiated directly with a UV radiation.
The above object may be achieved according to a first aspect of the present invention, which provides a mold assembly for forming an ophthalmic lens article such as an ophthalmic lens and an intermediate product for the ophthalmic lens. The mold assembly includes a first mold and a second mold, which are assembled together to define a mold cavity therebetween having a profile corresponding to that of the ophthalmic lens article. The mold cavity is filled with a polymeric material which is polymerized to form the ophthalmic lens article. At least one of the first and second molds is a resin mold which is formed of a resin material, a portion of at least a molding surface of the resin mold being irradiated directly with a UV radiation so as to provide a UV-treated surface. The ophthalmic lens article is formed in the mold cavity being held on the resin mold such that the ophthalmic lens article adheres to the UV-treated surface, when the first and second molds are separated away from each other.
In the mold assembly constructed according to the above first aspect of the present invention, a portion of at least a molding surface of one of the first and second molds, in which the mold is formed of a resin material, is irradiated directly with UV radiation so as to provide the UV-treated surface. The ophthalmic lens article formed in the mold cavity is held on the above-indicated one mold formed of the resin material (resin mold) such that the ophthalmic lens article adheres to the UV-treated surface of the resin mold every time the first and second molds are separated away from each other. In other words, in the present mold assembly, a portion of at least the molding surface of the resin mold is pre-treated by exposure to UV radiation, so as to provide the UV-treated surface to which the molded ophthalmic lens article adheres with high reliability.
In the present mold assembly, the molding surface of the resin mold is partially pre-treated for permitting the molded ophthalmic lens article to adhere to and be held on the resin mold, by using a UV-radiation emitting device which is available at a relatively low cost and safe to handle. Thus, there is no requirement to use the expensive corona-discharge device, which requires careful handling, as used in the conventional mold assembly described above. When the pre-treatment described above is effected, the UV-radiation emitting device can be located at any position provided that UV radiation is incident directly upon a desired portion of at least the molding surface of the resin mold, so that a UV lamp of the UV-radiation emitting device, for example, need not be positioned close to the resin mold. As compared with the prior art technique using the corona-discharge device, the present arrangement assures easy positioning of the UV-radiation emitting device as the pre-treating device, and protects the molding surface to be pre-treated from damage due to contact thereof with the UV lamp.
In the thus constructed mold assembly for forming the ophthalmic lens article, the molding surface of either one of the first and second molds is pre-treated for holding the molded ophthalmic lens article thereon, at a relatively low cost and in a safe and easy manner without a risk of damaging the molding surface, whereby an intended ophthalmic lens article can be formed at a minimized cost with high production efficiency.
In a preferred form of the above first aspect of the invention, only the molding surface of the resin mold is at least partially formed into the UV-treated surface. According to this arrangement, the ophthalmic lens article formed in the mold cavity adheres only to the molding surface of the resin mold when the first and second molds are separated away from each other, so that the ophthalmic lens article is held on the resin mold with high reliability.
When only the molding surface of the resin mold is formed into the UV-treated surface as described above, the molding surface of the resin mold includes an optical zone-defining region and a peripheral zone-defining region which give an optical zone and a peripheral zone of the ophthalmic lens article, respectively, and at least a portion of the peripheral zone-defining region is formed into the UV-treated surface.
According to the present arrangement, the molded ophthalmic lens article adheres to the molding surface of the resin mold only at its peripheral zone except for its optical zone, to thereby avoid possible damage to the optical zone of the ophthalmic lens article when the molded ophthalmic lens article is held on the resin mold. Accordingly, the ophthalmic lens article is capable of exhibiting intended optical characteristics.
In a preferred form of the above first aspect of the present invention, the first and second molds are both formed of a resin material, the first and second molds being assembled together to define therebetween a reservoir for storing an excess of the polymeric material which overflows the mold cavity. The reservoir is partially defined by a reservoir-defining surface of one of the first and second molds, and is different from the other mold which has a molding surface that is at least partially formed into the UV-treated surface. That is, only the reservoir-defining surface of the one mold, being at least partially formed into a UV-treated surface through direct irradiation with UV radiation, is partially formed into the UV-treated surface. Accordingly, excess polymerized product formed by polymerization of the excess polymeric material in the reservoir is held on the one mold such that the excess polymerized product adheres to the UV-treated surface of the one mold, when the first and second molds are separated away from each other.
According to this arrangement, when the first and second molds are separated away from each other, the ophthalmic lens article formed in the mold cavity adheres to and is held on the above-indicated other mold whose molding surface is at least partially formed into the UV-treated surface, while the excess polymerized product (excess polymer) formed by polymerization of the excess polymeric material in the reservoir adheres to and is held on the above-indicated one mold whose reservoir-defining surface is at least partially formed into the UV-treated surface. In this arrangement, the intended ophthalmic lens article and the excess polymerized product to be discarded is held on one and the other of the first and second molds, respectively, without an additional step of separating the ophthalmic lens article and the excess polymerized product from each other, resulting in improved production efficiency of the intended ophthalmic lens article.
In a preferred form of the above first aspect of the present invention, the first and second molds are irradiated with UV radiation with a portion of at least one of the first and second molds being covered with a shielding member which shields the portion from UV radiation, so that the other portion of the at least one of the first and second molds, which is not covered with the shielding member, is exposed to UV radiation, to thereby provide the UV-treated surface
In the present arrangement, the desired portion of the mold can be formed into the UV-treated surface in a considerably simplified and economical manner, without a troublesome and costly step of preparing electrodes having special configurations following those of the molds to be pre-treated, as in the conventional technique using the corona-discharge device. By using the present mold assembly described above, the intended ophthalmic lens article can be formed at a reduced cost with improved production efficiency.
In a preferred form of the above first aspect of the present invention, one of the first and second molds, on which the ophthalmic lens article is held such that the ophthalmic lens article adheres to the UV-treated surface, is a male mold while the other of the first and second molds is a female mold.
According to this arrangement, the formed ophthalmic lens article adheres to and is held on the male mold, so that the ophthalmic lens article can be easily removed from the UV-treated surface without being damaged, by simply collapsing the male mold.
In a preferred form of the above first aspect of the present invention, the UV-treated surface has been irradiated directly with UV radiation using an excimer lamp. This arrangement permits the UV-treated surface to exhibit a significantly enhanced adhesive strength for holding the ophthalmic lens article thereon.
In a preferred form of the above first aspect of the present invention, the UV-treated surface has been irradiated directly with UV-radiation having a wavelength within a range of 170xcx9c260 nm. Since UV radiation having a wavelength exceeding 260 nm has a low degree of photon energy, the UV-treated surface which has been irradiated with UV radiation whose wavelength exceeds 260 nm does not exhibit a sufficiently high adhesive strength for holding the ophthalmic lens article thereon. UV radiation whose wavelength is less than 170 nm tends to be absorbed in the atmosphere, increasing an attenuation factor of the irradiance of UV radiation with respect to a distance from the light source in the form of the UV lamp of the UV-radiation emitting device. To avoid this, the light source needs to be positioned as close as possible to the portion of the mold assembly to be treated with UV radiation. Alternatively, UV radiation needs to be applied to the above-indicated portion of the mold assembly such that the light source (UV-radiation emitting device) and the mold assembly are placed in vacuum by using a suitable vacuum device. In either case, there may arise problems of deteriorated production efficiency and increased cost of manufacture of the ophthalmic lens article. Accordingly, if the above-indicated portion of the mold assembly is irradiated with UV radiation having a wavelength of 170xcx9c260 nm, the portion of the mold assembly can be formed, in a simplified and economical manner, into the U-treated surface which exhibits significantly enhanced adhesive strength for holding the ophthalmic lens article thereon.
In a preferred form of the above first aspect of the invention, the UV-treated surface has been treated with UV radiation at a radiation energy of 0.1xcx9c5.5 mJ/cm2.
If UV radiation energy per unit area is less than 0.1 mJ/cm2, the UV-treated surface does not exhibit a sufficiently high adhesive strength for holding the ophthalmic lens article thereon. On the contrary, if UV radiation energy exceeds 5.5 mJ/cm2, the adhesive strength exhibited by the UV-treated surface is excessively large depending upon the wavelength of UV radiation applied thereto. In this case, it requires a special device or instrument for removing the ophthalmic lens article from the UV-treated surface, undesirably deteriorating the production efficiency and inevitably increasing the cost of manufacture of the ophthalmic lens article. Further, the ophthalmic lens article may receive an unexpected external force due to the use of the device or instrument upon removal from the UV-treated surface, undesirably causing a risk of damaging the ophthalmic lens article. In view of the above, if the UV-treated surface has been treated with UV radiation at a radiation energy of 0.1xcx9c5.5 mJ/cm2, the UV-treated surface exhibits a sufficiently high adhesive strength for holding the ophthalmic lens article thereon without requiring a troublesome and costly process of removing the ophthalmic lens article from the UV-treated surface.
The above-indicated second object of the present invention may be attained according to a second aspect of the invention, which provides a method of forming an ophthalmic lens article such as an ophthalmic lens and an intermediate product for the ophthalmic lens, by using the mold assembly as defined in the above first aspect of the invention. The method includes assembling the first and second molds together to thereby define the mold cavity therebetween, at least one of the first and second molds being the resin mold, and a portion of at least the molding surface of the resin mold being irradiated directly with UV radiation so as to provide the UV-treated surface; polymerizing the polymeric material filled in the mold cavity, to provide a polymer that gives the ophthalmic lens article; separating the first and second molds away from each other; and removing the ophthalmic lens article from the resin mold while the ophthalmic lens article is held on the resin mold such that the ophthalmic lens article adheres to the UV-treated surface of the resin mold.
In the method described above, the ophthalmic lens article is molded by using the mold assembly consisting of the first and second molds, one of which is a resin mold in which at least its molding surface is irradiated directly with UV radiation so as to provide the UV-treated surface. The molded ophthalmic lens article is held on the resin mold such that the ophthalmic lens article adheres to the UV-treated surface when the first and second molds are separated away from each other. Thereafter, the ophthalmic lens article adhering to the UV-treated surface is removed therefrom. According to this method, the formed ophthalmic lens article is held on the resin mold every time the first and second molds are separated away from each other, resulting in enhanced production efficiency of the ophthalmic lens article. In the present method, the portion of at least the molding surface of the resin mold is irradiated directly with UV radiation so as to provide the UV-treated surface for holding the formed ophthalmic lens article thereon. Thus, the present method permits the UV-treated molding surface to be economically formed in the molding surface in a simplified and safe manner without a risk of damaging the molding surface, as compared with the conventional method wherein the corona-discharge device is used to treat the molding surface. Further, the molding surfaces of the first and second molds of the mold assembly used in the present method need not have special surface configurations which enable the ophthalmic lens article to be held thereon, assuring a high degree of freedom in the configuration of the ophthalmic lens article formed between the molding surfaces. Thus, the present method permits the manufacture of the ophthalmic lens article having a desired configuration at a minimized cost with high efficiency.
In a preferred form of the above second aspect of the present invention, the step of removing the ophthalmic lens article held on the resin mold is effected by collapsing the resin mold radially inwardly, so that the ophthalmic lens article is removed from the UV-treated surface of the resin mold. This arrangement permits easy, quick, and economical removal of the ophthalmic lens article from the UV-treated surface without using a special device or instrument.
In a preferred form of the above second aspect of the present invention, the step of removing the ophthalmic lens article held on the resin mold is effected by immersing the ophthalmic lens article together with the resin mold in water for hydration, so that the ophthalmic lens article is removed from the V-treated surface of the resin mold. According to this arrangement, the ophthalmic lens article adhering to the UV-treated surface can be advantageously removed therefrom without being damaged due to an external force which would be otherwise applied to the ophthalmic lens article due to the use of the special device or instrument upon removal from the UV-treated surface.